Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.ServiceModel/System/ServiceModel/ConcurrencyMode.cs

@@ -0,0 +1,27 @@
+//------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+//------------------------------------------------------------
+
+namespace System.ServiceModel
+{
+    using System;
+
+    public enum ConcurrencyMode
+    {
+        Single, // This is first so it is ConcurrencyMode.default
+        Reentrant,
+        Multiple
+    }
+
+    static class ConcurrencyModeHelper
+    {
+        static public bool IsDefined(ConcurrencyMode x)
+        {
+            return
+                x == ConcurrencyMode.Single ||
+                x == ConcurrencyMode.Reentrant ||
+                x == ConcurrencyMode.Multiple ||
+                false;
+        }
+    }
+}